1. Field of the Invention
This invention relates to a portable light, particularly to torches, flashlights and the like.
2. Description of Related Art
Light emitting diodes (LEDs) are well-known as light sources. While more efficient than incandescent light bulbs at converting electrical power to light, LEDs can generally emit only low intensity light. LEDs are widely used as indicator lights or warning lights in instrument panels (e.g., in aircraft or in road vehicles). Recently LEDs have also been used as light sources in bicycle lamps, serving to give warning to other road users of the presence of the cyclist, and in key-ring lights.
LEDs are thus generally used for "passive" illumination, in which light emitted from the LED enters an observer's eye substantially directly, so as to confer information to the observer about the LED (e.g. on or off). It is very uncommon for LEDs to be used for "active" illumination, in which light emitted from the LED encounters an object and is reflected or otherwise re-directed from the object to an observer, so as to give information to the observer about the object rather than the LED. The reason for is the low intensity of light emitted from LEDs, as explained above, and because of the delicate nature of LEDs which are easily damaged, e.g., by exposing the LED to a current and/or voltage which exceeds the maximum values stated by LED manufacturers ("overrunning") the LED. It is well known to the person skilled in the art that overrunning of LEDs should be avoided because it can cause the LED to burn out or fail, or else substantially shorten the working life of the LED.